EFFECS OF CLOSURE STRESS ON FRACTURE MORPHOLOGY AND MULTI-PHASE FLOW IN SHEAR FRACTURED BEREA SANDSTONE

Open Access
Author:
Al Enezi, Sultan Mohammad
Graduate Program:
Petroleum and Natural Gas Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 02, 2009
Committee Members:
  • Phillip Michael Halleck, Dissertation Advisor
  • Phillip Michael Halleck, Committee Chair
  • Abraham Grader, Committee Member
  • Derek Elsworth, Committee Member
  • Zuleima T Karpyn, Committee Member
  • Demian Saffer, Committee Member
Keywords:
  • shear fracture
  • fluid flow
Abstract:
Understanding the mechanical properties of fractures and how fractures affect single and multi-phase flow behavior is very important, not only in petroleum reservoirs but also in many other fields. Multi-phase flow behavior in shear fractures is not fully understood. This study focuses, on fracture morphology and hydraulic behavior of a shear fracture, along with the effects of closure stress. Morphology of the shear fracture and the effects of increasing the closure stress on fracture properties were studied under dry condition using high resolution Micro-Computed Tomography (MCT). Fracture properties such as average aperture and asperity ratio are highly affected by increasing the closure stress. Two multi-phase flow experiments were conducted under two different closure stresses. Full scans were acquired at different saturation conditions at both closure stresses. High effective oil permeability combined with low Swirr in the fracture and high Swirr in the matrix, indicates that the fracture is acting as an oil conduct. Increasing the closure stress has no significant effect on the fluid distributions inside the fracture and on effective permeabilities; the same behavior was observed at both closure stresses. Fluid distributions at all saturation conditions and at both closure stresses confirm that oil occupies the large apertures; and cannot be displaced out of the fracture and force the water to flow in the matrix and the small apertures, thus yielding very low water relative permeabilities at Sor. The saturations in the matrix adjacent to the fracture were calculated and compared to the saturations in the fracture. Increasing water saturation was observed going from the fracture into the wall and further matrix at both Swirr and Sor conditions.